Abstract

Purpose

We report the first clinicopathological series of longitudinal FDG-PET scans in post-mortem (PM) verified cognitively normal elderly (NL) followed to the onset of Alzheimer’s-type dementia (DAT), and in patients with mild DAT with progressive cognitive deterioration.

Methods

Four NL subjects and three patients with mild DAT received longitudinal clinical, neuropsychological and dynamic FDG-PET examinations with arterial input functions. NL subjects were followed for 13 ± 5 years, received FDG-PET examinations over 7 ± 2 years, and autopsy 6 ± 3 years after the last FDG-PET. Two NL declined to mild cognitive impairment (MCI), and two developed probable DAT before death. DAT patients were followed for 9 ± 3 years, received FDG-PET examinations over 3 ± 2 years, and autopsy 7 ± 1 years after the last FDG-PET. Two DAT patients progressed to moderate-to-severe dementia and one developed vascular dementia.

Results

The two NL subjects who declined to DAT received a PM diagnosis of definite AD. Their FDG-PET scans indicated a progression of deficits in the cerebral metabolic rate for glucose (CMRglc) from the hippocampus to the parietotemporal and posterior cingulate cortices. One DAT patient showed AD with diffuse Lewy body disease (LBD) at PM, and her last in vivo PET was indicative of possible LBD for the presence of occipital as well as parietotemporal hypometabolism.

Conclusion

Progressive CMRglc reductions on FDG-PET occur years in advance of clinical DAT symptoms in patients with pathologically verified disease. The FDG-PET profiles in life were consistent with the PM diagnosis.

FDG-PET scans showing medial temporal lobe (MTL) hypometabolism for each subject at the last PET scan, as compared to a healthy control with normal MTL CMRglc. The scans are reformatted to a plane parallel to the plane of the temporal lobe, a plane that runs approximately parallel to the long axis of the hippocampus at an infraorbital angulation of 20° to 25° negative to the canthomeatal plane. This axial orientation enables examination of the full anterior–posterior extent of the hippocampal region and most of the parahippocampal gyrus (Mosconi et al; Eur J Nucl Med Mol Imaging 2006; 33:210–21). CMRglc values are represented on a color-coded scale ranging from 0 to 50 μmol/100 g per minute (DOC 551 KB).

The National Institute on Aging, the Reagan Institute Working Group on Diagnostic Criteria for the Neuropathological Assessment of Alzheimer’s disease. Consensus recommendations for the postmortem diagnosis of Alzheimer’s disease. Neurobiol Aging 1997;18:S1–2.View Article